Thread: DC/DC CTEK D250S Dual in D4

Originally Posted by Javii_V7_I

Hi;

I wanted to ask you that you think the DC / DC Dual CTEK D250S for connecting an auxiliary battery in the D4.
Do you think it will work with the new charging system of D4?. From what I read is important to connect the negative ground terminal and the negative terminal of the main battery, but they are still operating according to the main battery voltage, so my question


(Sorry for my english)

Hi Javi,

Welcome to the forum.

In general, DC to DC type dual battery systems seem ideal for the D4. There are a lot of different views on this forum and this is my view. I prefer the DC to DC converters because they give the correct multi-stage charging that helps the auxiliary battery to charge more completely and to last longer.

However, the specs on the D250S do not specify that the starter battery is automatically disconnected when the car engine is stopped. It seems that you also need to fit the Ctek SmartPass to isolate and protect the starter battery. With the complex electronics in the D4, draining the starter battery can mean trouble.

The SmartPass is expensive. You can do a similar thing with a cheap automotive relay that only connects the D250S to the starter battery when the D4 ignition is switched on.

Most important though see this post from Drivesafe - he shows you where to connect the negative lead. http://www.aulro.com/afvb/d3-d4-rrs/...-warnings.html

Cheers,

Paul

DC/DC chargers are fine for the D4 just more expensive than other options.

Hi Javii and welcome to AULRO.

What sort of battery are you going to use as your auxiliary and where are you mounting it?

Hi, and thanks for the responses.

On the issue of the CTEK not disconnect when the car is stopped, thought about putting a relay fix. But I'm not sure that a system DC / DC which is based on the voltage of the starter battery to function properly in these new D4. Is that it worked properly RoverLander (with redarc) after connecting the negative terminal to ground and the negative terminal of the main battery, but I still have clear because this meant the improvement.

Regarding the battery had thought to put an Optima Yellow Top 4.2 (55 Ah) in the engine box, if I can change the ECU and wiring in place.

Cheers,

Hi again Javii, there is a link below to the VERANDAH section on this site and this will give you an idea of how you can set up your D4.

The kit is for a D3 but if you move the ECU, the kit is exactly the same for a D4.

Because you are going to use an Optima Battery ( the Optima D34 is the correct battery for the D4 ) you are far better off not using a DC-DC device because the Optima Yellow Top can take full inrush currents when charging and combine this with the way the D4 charges, you nearly fully charge an Optima battery from a low state in about an hours driving.

I’ve measured up to 64 amps going into a low Optima and a D3 owner in the UK has measured up to 97 amps going into his Optima when the battery was near flat.

DC-DC devices just can’t handle these sorts of load and again, the way both a D4 charges and the way an Optima can be charged, just mating the two, via a decent isolator will give you the best set up.

Again, the kit in this link will give you an idea of the way to set up your D4 and I supply these kit world wide.


http://www.aulro.com/afvb/verandah/6...le-kit-d3.html

Originally Posted by Javii_V7_I

Hi, and thanks for the responses.

On the issue of the CTEK not disconnect when the car is stopped, thought about putting a relay fix. But I'm not sure that a system DC / DC which is based on the voltage of the starter battery to function properly in these new D4. Is that it worked properly RoverLander (with redarc) after connecting the negative terminal to ground and the negative terminal of the main battery, but I still have clear because this meant the improvement.

Regarding the battery had thought to put an Optima Yellow Top 4.2 (55 Ah) in the engine box, if I can change the ECU and wiring in place.

Cheers,

Hi Javi,

The DC - DC system will work properly regardless of the starter battery voltage. That is the best reason to go for the DC-DC - they charge properly whatever the starting battery voltage.

Also, in my experience alternators can be damaged by excessive current draw - with both the starter battery and the auxiliary battery drawing high current it puts a big load on the alternator. In my experience this reduces alternator life, maybe as little as five years.

The relay fix and the D250S should work very well for you.

Cheers,

Paul

So what your saying Wilbur, is by adding a DC-DC device to the set up you now have a better system.

Well your math does not add up.

To add a DC-DC device to a D4 set up means the Optima battery if low will actually far take longer to fully charge than when using nothing more than a standard isolator.

Next, with your suggested set, you need to spend far more to get less available battery capacity.

Your set up give 44Ah of usable battery capacity while an SC80-LR gives at least 85Ah for a lower set up cost and this 85 Ah will be replaced far quicker than your DC-DC device can do it.

As to alternator use, with the 180 amp alternators in a D4, are suggesting that even if a battery pulled 90 amps while charging then the alternator is going to be damaged.

Tell me then why the same alleged damage has not happened in D3s with their smaller 140 amp alternators.

You do like to make up mythical problems, don’t you Wilbur?

Originally Posted by drivesafe

So what your saying Wilbur, is by adding a DC-DC device to the set up you now have a better system.

Well your math does not add up.

To add a DC-DC device to a D4 set up means the Optima battery if low will actually far take longer to fully charge than when using nothing more than a standard isolator.

Next, with your suggested set, you need to spend far more to get less available battery capacity.

Your set up give 44Ah of usable battery capacity while an SC80-LR gives at least 85Ah for a lower set up cost and this 85 Ah will be replaced far quicker than your DC-DC device can do it.

As to alternator use, with the 180 amp alternators in a D4, are suggesting that even if a battery pulled 90 amps while charging then the alternator is going to be damaged.

Tell me then why the same alleged damage has not happened in D3s with their smaller 140 amp alternators.

You do like to make up mythical problems, don’t you Wilbur?

Hi Drivesafe,

No, I don't think I am making up mythical problems. You see, if the auxiliary battery takes 90 amps the starter battery will also be taking current, and this could be getting close to the maximum alternator rating. ~Rich~ had to replace his alternator at 5 years - see http://www.aulro.com/afvb/d3-d4-rrs/...g-voltage.html Maybe if he had been using a DC - DC system that put less load on the alternator than the Traxide this would not have happened.

Yes, I do understand that the Traxide system gives more usable power for the auxiliary loads than any other system because it also drains the starter battery into the auxiliary loads. For those not worried by this, the Traxide is great, and has been proven over the years.

However, for those who don't want to drain their starting battery, I believe the DC - DC system is the best and well worth the extra money.

Cheers,

Paul